The invention is based on an electromagnetic device, in particular for a slip-controlled, hydraulic vehicle brake system, as generically defined by the preamble to claim 1.
One such device is known from European Patent Disclosure EP 0 675 030 A2. A valve block used there has a plurality of receiving bores, in which first magnet valves, which are closed in the currentless basic position, and second magnet valves, which are open in the currentless basic position, are received on valve carriers. The first and second magnet valves each have a hydraulic part, with a valve closing member that is controlled by a magnet armature and is movable relative both to a valve seat body, retained by a valve seat carrier, and to a pole piece, and an electrical part, with a magnet coil, which in the electrically excited state cooperates with the magnet armature in such a way that the first magnet valve is opened and the second magnet valve is closed.
For receiving the first and second magnet valves in the receiving bores of the known valve block, a retaining plate is provided, which keeps the respective valve carrier in the receiving bore and is screwed to the valve block. The retaining plate has through bores, through which guide sleeves of the magnet valves protrude. A magnet coil is placed on the respective part of a guide sleeve protruding from the retaining plate and surrounds it. The magnet coil is embraced by a yoke.
In a guide sleeve, a pole piece, a valve spring, and a magnet armature with a closing body of a seat valve are all received. The guide sleeve comprises a nonferromagnetic material and is widened at the end into a flange, which on the face end rests on a valve seat carrier and over which the valve carrier fits. The valve carrier and the valve seat carrier are joined together by a crimped connection.
The known device has the disadvantage that the magnet valves cannot be inserted as completely preassembled structural units into the receiving bores, since first the guide sleeve together with the valve carrier and the valve seat carrier must be fixed in the receiving bore by means of the retaining plate, and only then must the magnet coil be placed on the guide sleeve together with the yoke.
Furthermore, the first and second magnet valves are relatively long and protrude out of the receiving bores of the valve block, and as a result the control unit of the known electromagnetic device, which carries the valve block, is relatively tall. Furthermore, the installation depth and hence the installation rigidity of the guide sleeves, which protrude far out of the receiving bores and absorb the dynamic forces resulting from the motion of the magnet armature, are slight.
Finally, the guide sleeve is of nonferromagnetic material and is disposed within the primary magnetic flux. This has the disadvantage that the guide sleeve represents a high magnetic resistance, which thus weakens the magnetic flux.
The electromagnetic device of the invention having the characteristics of claim 1 has the advantage over the prior art that because of the one-piece valve housing, which surrounds all the magnet valve components, the first and second magnet valves can each be inserted as completely preassembled units into the receiving bores. This also lends high intrinsic rigidity to the magnet valves, which is especially advantageous whenever they are wedged in the receiving bores by major exertion of force and the high intrinsic rigidity prevents the preset valve play from changing as a result of relative motions of magnet valve components to one another and prevents the magnet armature from wedging in its guide. Since for both types of magnet valve, those that are open without current and closed without current, the same one-piece valve housing is used, the number of different components is reduced, which has a favorable effect on the production costs.
Further advantages will become apparent from the countersunk arrangement of magnet valves in the receiving bores of the valve block. The result on the one hand is greater installed rigidity of the magnet valves in the receiving bores, and on the other, the result is also that the heat-producing magnet coils are disposed in countersunk fashion, and the heat dissipation can take place through the valve block. Because of this provision, heat-sensitive electronic control components can be disposed in direction end-to-end contact with the countersunk magnet valves, which reduces the structural size of the control unit of the device.
Finally, the nonferromagnetic spacer ring has an advantageous dual function. First, it seals off the hydraulic part of the magnet valves, which is acted upon by pressure medium and contains the magnet armature, the valve closing member, the valve seat carrier, and the pole piece, from the electrical part having the magnet coil. Second, by its arrangement between the face end of the magnet coil toward the valve seat and the dividing plane between this magnet coil and the associated pole piece, it is not located inside the primary magnetic field, and thus its magnetic resistance exerted on the magnetic field is correspondingly slight. In addition, the nonferromagnetic spacer ring does not short-circuit the magnetic field lines to the valve housing, but instead assures that these field lines can penetrate the magnet armature of the first magnet valve and the pole disk of the second magnet valve.
By combining these provisions, the result overall is a very rigid, short design of the first and second magnet valves, and as a result the control unit of the electromagnetic device is small in size. Moreover, the magnet valves comprise only a few components.
By means of the provisions recited in the dependent claims, advantageous refinements of and improvements to the electromagnetic device defined by claim are possible.
It is especially advantageous that the valve seat bodies of the first and second magnet valves are embodied structurally identically and each in one piece with the valve seat. This further reduces the number of different components.
An especially preferred refinement of the invention provides that a first nonferromagnetic spacer ring is disposed in the radial direction between the valve housing and the pole core; this ring protrudes axially past an end face, pointing toward the first magnet armature, of the pole core with an annular portion on its face end, on which portion the first magnet armature rests when the first magnet valve is opened. As a result, a remanent air gap between the pole piece and the magnet armature is assured, which prevents magnetic adhesion of the magnet armature to the pole piece.